1. Field of the Invention
The present invention relates to novel silicon-based compositions and the use thereof. In particular, the invention concerns novel film forming compositions that have properties suitable for anti-reflective coatings used in lithographic fabrication of semiconductor devices. The present invention also concerns methods of producing anti-reflective coatings on substrates.
2. Description of Related Art
There is a constant demand for decreasing the size of various features in semiconductor devices, e.g. integrated circuits (ICs). This demand creates challenges for the manufacturing processes. Photolithography is an example of a technique commonly used for the production of such devices and in particular for creating the patterns that define structures in ICs. In a lithographic process, a layer of a photoresist material is deposited on a substrate. The photoresist layer is selectively exposed to radiation, such as ultraviolet-light or electrons, and an exposure tool and mask are used for producing the desired selective exposure. The patterns in the resist are then created when the wafer undergoes a subsequent “development” step. The areas of resist that remain after development serve to protect the substrate regions which they cover. Locations from which resist has been removed can be subjected to a variety of subtractive or additive processes that transfer the pattern onto the substrate surface.
Generally, the substrate surfaces commonly used are highly reflective. The light-waves used in the exposure propagate through the photoresist film down to the substrate, and are reflected back up through the photoresist. This causes off-normal reflection effects and standing wave effects. These effects give rise to significant and critical variations in the dimensions of the patterns, and several techniques have been developed to suppress them, including the use of anti-reflective coatings (in the following also abbreviated “ARC”s) fitted below or above the resist layer. Methods that reduce reflectivity at the resist interfaces can provide line width control with minimal loss of resist performance. For example, anti-reflection coatings can be used to dampen the reflections. The reflections are suppressed either by attenuating the light that passes through the ARC, or by matching the index of refraction of the ARC to the resist system at the exposure wavelength employed such that destructive interference of the light passing through the ARC occurs. The use of ARCs has become essential for allowing optical-lithography to be used in fabrication of features smaller than 0.5 μm. The ARC layer needs to fulfil several properties, such as a predetermined extinction coefficient (k, ability to absorb energy of the radiation) at the used exposure radiation, refractive index (n), film thickness, dry and wet etching properties (compositional property), adhesion, process and material compatibility and stability of final material.
There is a need for new materials that will provide a combination of good optical properties and sufficient thermal and mechanical durability and strength.